Methylation analysis polysaccharide

The floss silk from Chorisia speciosa furnished a polysaccharide with a main chain of (1 -> 4) linked P-Xylp substituted at 0-2 by 5 % of uronic acid. The xylan structure also was interposed with a-Rhap units in small amounts. The defatted seeds furnished on aqueous extraction a major fraction, ((9-acetyl, 10 % and protein, 45 %) wich was hydrolysed and analysed by p.c. and GLC, showing Rha (20 %), Ara (16 %), Gal (64 %) and also uronic acids (45 %). Partial hydrolysis gave rise to a polysaccharide free of arabinose, with 46 % of uronic acids. Methylation analysis (GLC -MS) indicated a chain of (1 4) - linked Gal/ (42 % of 2,3,6-Me3-Gal). 

Methylation analysis of PI and FIbp. The fractions were methylated according to Ciucanu and Kerek [8]. The procedure was repeated until no absorbance was detected by I.r. at 2500-3500 cm-i and the per-O-methylated polysaccharides hydrolyzed and analyzed by GLC and GLC-MS of the derived partly O-methylated alditol acetates. 

The aim of this project is to get additional information about the fine structure of pectic polysaccharides. Therefore pectins from red beet were isolated and fractionateid by chromatographic methods. Some results obtained by methylation analysis of these pectin-rich fractions are presented. 

Kvemheim, A.L. (1987). Methylation analysis of polysaccharides with butyllithium in dimethyl sulfoxide. Acta Chem. Scand. Ser. B41,150-152. 

Most early publications on bacterial polysaccharides were concerned with impure products and poorly-described organisms. Many more recent papers are of limited value also, due to low yields, lack of characterization of products and arbitrary interpretations of data. Low yields of methylated polysaccharides may be due to degradation of the bacterial polysaccharide during methylation, or to degradation of the hydrolytic products of the methylated polysaccharide (to form methyl levulinate, etc.46). The great importance of (a) complete methylation of polysaccharide products prior to structural determination by hydrolysis and (6) quantitative identification of the hydrolytic products, has been emphasized previously. Other difficulties in end group analysis have been discussed recently.7... 

Figure 3 shows the structure of the hemicellulosic polysaccharides obtained from the bran cell wall preparations. These structures were deduced from the results of the methylation analysis of purified fractions (13). In contrast to the endosperm cell wall, no / -l,3-,l,4-glucan was obtained from... 

Figure 3. Structure of hemicellulosic polysaccharides obtained from rice bran, (a) Deduced from the results of methylation analysis described in ref. 13.

Similarly, methylation analysis of a partially hydrolyzed sample of the Klebsiella type 38 capsular polysaccharide, composed of pentasaccharide repeating units (5), revealed that the terminal 3-deoxy-L-g/ycero-pentulosylonic acid group (6) was located at 0-3 of a D-galac-tosyl residue (7), as the 6-O-methyl-D-galactose in the methylation... 

Oxidation of the carboxyl-reduced and acetylated Pneumococcus type 2 capsular polysaccharide revealed that only one L-rhamnose residue in the hexasaccharide repeating-unit, later demonstrated to have the structure 60, was oxidized and, consequently, /3-L-linked.156 Replacement of 2,3,6-tri-O-methyl-D-glucose in the methylation analysis of the original polysaccharide by 2,3,4,6-tetra-O-methyl-D-glucose in that of the oxidized polysaccharide established that this L-rhamnose residue is linked to 0-4 of a D-glucose residue. The analysis also showed that it was an L-rhamnose residue in the chain (and not the branching L-rhamnose residue) that was /3-linked. 

The structures of oligosaccharides and polysaccharides are usually determined by a combination of methods specific enzymatic hydrolysis to determine stereochemistry and produce smaller fragments for further analysis methylation analysis to locate glycosidic bonds and stepwise degradation to determine sequence and configuration of anomeric carbons. 

The polyarabinose preparation ([a]Jj + 27.1°) of Mora and coworkers174 was subjected to methylation analysis by Dutton and Unrau.1 0 In common with other synthetic polysaccharides prepared by this method, the poly-arabinose had a highly ramified structure 16% of the nonreducing end-groups of the polysaccharide were furanoid, as indicated by the isolation of... 

The extracellular polysaccharides of Rhizobium meliloti 201 have been examined by using enzymic degradation and chemical procedures.314 A mixture of polysaccharides produced by the bacterium, when incubated with a bacterial enzyme that hydrolyzed one of these, gave oligosaccharides that could be separated by DEAE-cellulose chromatography. The major fraction was a pentasaccharide, for which methylation analysis and Smith... 

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